Grid manufacture



Aug. 25, 1964 s, MacARTHUR 3,145,740

GRID MANUFACTURE Filed May 51, 1961 2 Sheets-Sheet 1 INVENTOR CURTIS SZMAC ARTHUR a, wm. PM

ATTORNEY Aug. 25, 1964 Filed May 31, 1961 c. s. M ARTHUR 3,145,740

GRID MANUFACTURE 2 Sheets-Sheet 2 IN VE N TOR CURTIS .5. MA 0 ARTHUR ATTORNEY United States Patent Filed May 31, 1961, Ser. No. 113,799 4 Claims. (Cl. 140-415) This invention relates generally to wound type grid electrodes such as are used in receiving tubes and other types of electrical space discharge devices and, more particularly, to an improvement in the manufacture of such grids and to the resulting grid structure.

A common procedure for making grids comprises first indenting a support rod with a cutting tool, leading the grid wire into the indentation, and then securing the wire in the indentation by striking the support rod at the indentation with a second tool called a swedging tool. This method has inherent limitations and cannot produce grids having a high number of turns per inch. It further tends to introduce a bow in the support rods and, in many cases, if the first and second tools are not properly aligned, an unreasonably high number of loose grid wires are produced, leading to rejects and increased production.

costs.

In an eifort to overcome these difficulties, a second method was tried. Generally, this consists of cutting slots in the supports or side rods by rotating a mandrel carrying the side rods past a U-shaped wheel cutter which, when making a cut, also secures the grid wire which has been laid in a previously made slot. This method has also been found to have several major difficulties, not the least of which is the distortion of the side rod by the upward or transverse plowing action of the cutting wheel. An additional difliculty is that, in order to accommodate grid wires of different diameters, the angle of the cutting edge of the wheel has to be varied, thereby necessitating frequent adjustment when it is desired to make different size grids. A further difliculty encountered is that the transverse plowing action of the cutting Wheel also causes a ridge of metal to appear on the upper edge of the cut and, when the grid wire is placed in the cut, this ridge causes the grid wire to slip to one side or the other, thereby resulting in uneven, non-parallel spacing of the individual laterals of the grid wire. Again, this spacing is also further misaligned by the transverse plowing action of the cutting wheel as it makes the next adjacent slot.

The present invention avoids all thte diiiiculties of prior art procedures, reduces the number of operations required to form a grid, and allows grids having the higher number of turns per inch to be produced than v ere able to be produced in the prior art. My invention is such that more uniform, well-formed grids can be obtained by eliminating entirely the separate peening or swedging operation in such a way that uniform, parallelrid wire spacing can be achieved, thereby aiding in avoiding the disadvantages introduced by transverse relative motion between the cutting tool and the side rods as the cuts are being made.

Briefly described, the making of grids by my invention comprises forming a first notch by indenting a side rod with a V-shaped notching tool which is disposed perpendicular to the center line of the side rod and in the same lane as the mandrel carrying the side rod Without introducing relative transverse motion between the tool and the side rod as the ndentation is'rnade, leading the grid Wire into the notch made by the tool, and securing the; wire in the notch during the formation oi the following notch in the side 'rod in the same manner as the first notch is formed. Themaking of the second notch causes the material between the first and second notch to'be dis- 3,145,?40 Patented Aug. 25, 1964 placed an amount such that the wire is firmly secured in the first notch.

The invention will be better understood as the following description proceeds, taken in conjunction With the accompanying drawings, wherein:

FIG. 1 is an elevational view of a grid in the process of fabrication in accordance with the invention;

FIG. 2 is a sectional view taken along the line 2--2 of FIG. 1;

FIG. 3 is an enlarged plan view of a cutting tool useful in carrying out the present invention;

FIG. 4 is a side View of the tool of F IG.

FIG. 5 is a greatly enlarged view of the simultaneous notching and peening action of one of the tools as it acts on the side rod; and

FIG. 6 is a partially sectioned schematic end view of the action of the winding head in winding the grid of FIG. 1.

Referring now to the drawing and, more particularly, to FIG. 1, there is illustrated a grid in the process of fabrication according to my invention. Preferably, the grid is made on a grid-making machine of the type in which the mandrel 8 supporting the side rods 1 and 2 does not rotate during winding of the grid, the details of such a machine being set forth in Patent No. 2,181,288, issued November 28, 1939, to H. M. Washburn and assigned to the same assignee as the present invention. The grid structure, itself, comprises at least two side rods 1 and 2 which are provided with a plurality of notches, some of which are indicated at 3, 3', 3" and 4, t, 4" respectively. The grid wire 5 is wound around the side rods and the end loops of the individual laterals are positioned and secured in successive notches which are spaced evenly and uniformly throughout the length of the grid. Two notching tools, 6 and 7, in accordance with my invention, are illustrated on either side of the side rods. These tools are illustrated in more detail in FIGS. 3 and 4. The side rods 1 and 2 are supported in spaced relationship during the notching and winding operation by a preshaped mandrel S which is fixed in the plane of the notching tools 6 and 7. As shown more clearly in FIG. 2, the mandrel edges are grooved at 4'0 and St) to receive the side rods in slidable relation so that the side rods may be advanced along the mandrel during the formation of the grid. The notches 3, 3', 3 and 4-, 4, i" are formed alternately in succession, one in one side rod, one in the other side rod, as the operation proceeds.

As shown more clearly in FIG. 6, the cuts or notches in the side rods are simultaneously formed with the winding of the grid wire 5, that is, when the winding head 3%, which is supplying the grid wire, is perpendicular to the upper side of mandrel 8, a first notch 4 is formed in side rod 2 by means of the cutting tool 7 moving in to contact the side rod 2. It will benoted that as the tool 7 moves inwardly to cut rod 2 the motion of the tool with respect to the side rod 2 is substantially longitudinal, i.e., there is no transverse relative motion in an up and down direction between rod 2 and the cutting edge of the tool 7 as the notch is formed. It has been found that this type of cutting action is particularly effective in preventing the formation of ridges along the notches such as occurs when cuts are made while transverse relative motion is taking place between the side rod and the tool. It is believed that this is a major contributing factor to the vastly superior grid structures with respect, particularly, to straightness and uniformity of winding, which are attainable in accordance with the present invention. As the head continues to rotate around the fixed mandrel 8 to a point from its initial starting position, the tool 7 is withdrawn from the notch 4 and the grid wire 5 is laid in the formed notch, and a similar notch 3 is formed in the side rod 1 by means of tool 6 moving in and striking side rod 1, the notches in the two side rods being successively formed and being staggered with respect to each other a distance equal to the longitudinal advance of the side rods as they are slowly drawn along the mandrel 8, past the tool position. The rate of the longitudinal advance of the side rods 1 and 2 along the mandrel 8 past the tool position determines the spacing of the grid wire 5. The grid wire 5, as the winding head 30 rotates around the mandrel 8, is fed into each of the said notches which have been formed in the side rods. Thus, as the winding head 30 rotates, it supplies the grid wire to the notch 4 in side rod 2 and, when 90 from the other side rod 1, the notch 3 is being formed in side rod 1 by the notching tool 6 and then, as the winding head continues to pass around the mandrel 8, it supplies the grid wire 5 to the notch 3 formed in the side rod 1 by the tool 6. The winding head has now completed one revolution of 360 and is back to its initial starting position. Then, as the winding head 30 continues to rotate around the mandrel a second time, a notch 4' is made in the side rod 2 by the tool 7. The making of notch 4' moves side rod material toward notch 4 so that the grid wire 5, previously placed in notch 4, is secured therein. As the winding head continues to rotate around the mandrel, the grid wire is fed into notch 4' formed in the side rod 2 and a notch 3' is made in side rod 1 which tends to close notch 3 so that the grid wire previously placed in notch 3 is also secured therein. Thus, the grid wire is fed into the latest-cut notch 90", or one quarter revolution, after the notchs formation by the notching tool, and is secured therein by the making of a neighboring notch one revolution later.

In one specific form of notching tool, as shown in FIG. 3, the leading edge 23 is preferably made at an angle 5 from the perpendicular wall 24, and the trailing edge 25 is preferably made at an angle of 20 from the perpendicular wall 26, so that the edges meet in an apex and form a sharp V, which has an angle of 25 between the edges. The sharp V cutting edge of the tool described enables this tool to be used for grid wires of any size without changing the tool whereas prior art approaches necessitated the use of a different tool for different grid wire diameter. To accommodate grid wires of various diameters, all that is required is that the tools 6 and 7 be set for either a deeper or shallower cut into its respective side rod.

It has been found that the peening operation, and other difiiculties encountered in the prior art procedures, may be entirely eliminated by forming the notches 3 and 4 of the shape more particularly illustrated in FIG. 5, each notch having a trailing edge 11 and a leading edge 12 with the bottom of the notch having a sharp V formation. The wall surface 14 is moved toward the right in FIGS. 1 and 5 to occupy a position 13 by the creation of the next succeeding notch in the same side rod. Thus, each preceding notch in the same side rod is partially closed by the notching action of the tool so as to firmly grip the grid lateral 5 without the necessity of any conventional peening action or operation and, moreover, without upsetting or distorting, to any appreciable extent, the surface of the side rod.

In the particular embodiment shown in FIG. 5, the notching tool 6 is preferably disposed at an angle of 91 /22 to the center line of the support rod and is in the plane of the mandrel 8. However, this angle may be varied from 90 by a factor of plus or minus two degrees and still be effective. Any variation greater than this requires a change in the angles of edges 23 and 25. As described, the leading edge 16 of the tool is made at an angle of 5 with the tool surface 18 while the trailing edge 17 of the tool is made at an angle of 20 with the tools surface 19. Thus, the notch formed by tool 6 has one wall of the V at an angle of approximately 6 /2 with respect to a transverse imaginary plane perpendicular to the open end of the notch and passing through the apex of the notch, while the other wall is at an angle of approximately 18 /2" with respect to this plane. Excellent results have been obtained with this arrangement although, as pointed out above, other variations are possible as long as the angles of edges 23 and 25 are changed to coact with the new position of the tool. Of course, the foregoing also applies to tool 7.

The grid Wire 5, as it is lead by the winding head 30 into the notch 3 previously formed by the tool 6, is firmly abutted against both sides of the notch and, when the following notch is formed, is, by the movement of the material between the notches, firrnly secured in place. The diameter of the grid wire may be of any size without necessitating a change in angle of the tool 6 which is one of the benefits of this type of operation since, with wires of small diameter, a shallow notch is required while, with wires of a larger diameter, a deeper notch is required. It is evident that the notches formed by the particular tool, as shown here for illustration, are in section triangular in shape when made, but the shape of these notches is changed by the formation of the next successive notch which moves the body of material 21 to the right to clamp the grid wire 5 firmly and securely in place. The movement of the bodies of material 20 at the outer surface of the support rod is represented by the angle between dotted line 14 and position 13.

In accordance with the present invention, it has been found practical to construct grids having from to 1000 turns per inch without any distortion of the side rods, or of the grid wire spacing, and without changing the notching tool. Moreover, the troublesome and difiicult separate peening operation has been eliminated with a considerable savings in production costs being realized. It has been further found that by controlling the depth of the notch to accommodate the grid wire being used to form the grid and by using tools as shown herein instead of cutting Wheels that troublesome distortion in the side rods is avoided. For example, to build a grid having 120 turns per inch, it has been found that side rods of .030 inch diameter may be used with a grid wire of .0025 inch diameter and the depth of the notch would vary between .010 inch and .015 inch, depending on the hardness of the side rod material. It has further been found that wide variations in these dimensions are possible when making grids without changing the shape of the tool. Grids have been successfully built using grid wires having diameters as small as .0005 inch and as large as .005 inch on side rods that varied in diameter from .015 inch to .040 inch. In such cases, the depth of the notch varied from .005 inch to .020 inch. Previously, it was found that with both indenting and peening operation and with the cutting operation, as was practiced in the prior art, a bending took place which caused the side rods to bow. It has also been found, with the elimination of the peening operation as practiced in the prior art, that each and every grid wire is securely and tightly held in place. Moreover, the new and improved tool has a notching angle such that it has a greatly increased life and may be used with a multiplicity of grid wire sizes. Further, the entire machine is simplified since the winding of the grid wire follows the notching by about one-quarter revolution, or and no correlation or fine adjusting of a peening tool need be made with respect to the notching tool, nor need the tool be changed as the size of the grid wire is changed. Another important advantage is that exceedingly fine grid structures may be fabricated which were not feasible or possible where a peening tool was required to strike the notch after the wire had been placed into it, since separate peening and notching tools did not have sufficient room for interplay in the exceedingly fine area which is required for high-turn grids.

Although there have been described what are considered to be preferred embodiments of the present invention, various adaptions and modifications thereof may b made without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

1. The method of making a grid structure comprising supporting a pair of side rods in substantially parallel relation in a given fixed plane, disposing a cutting tool for movement along a given path in said plane toward and aWay from a side rod, moving said tool along said path in said plane into engagement with said rod to form a notch therein, guiding a grid wire into said notch, moving said side rod longitudinally in said plane to position an unnotched surface opposite the tool, moving the tool in said given path in said plane into engagement with the unnotched surface of the rod to form a succeeding notch in the rod sufficiently close enough to the preceding notch to simultaneously cause the material of the rod to be forced toward the preceding notch whereby the grid wire is wedged in the notch, and repeating the steps of moving the tool and guiding the grid wire to form successive notches in the rod having the grid Wire secured therein.

2. The method of making a grid structure according to claim 1 wherein each of the V-shaped notches is formed with one wall at an angle of approximately 6 /2 with respect to a transverse imaginary plane perpendicular to the open end of the notch and passing through the apex of the notch and the other wall of said notch forms an angle of approximately 18 with respect to said plane.

3. The method of making a grid structure comprising supporting at least two side rods in spaced substantially parallel relationship in a given fixed plane, moving notching tools along a given path in said plane into engagement with said side rods to form notches in each of said side rods while maintaining said side rods free from rotational transverse motion, guiding a grid wire into said notches alternately in said rods prior to the formation of successive notches by said tools, moving said side rods longitudinally in said plane to position an unnotched surface opposite said tools, and subsequently moving said tools in said plane into engagement with the unnotched surface of said rods to form succeeding notches and to simultaneously constrict the adjacent, previously-formed notches whereby the grid wire is wedged therein.

4. The method of making a grid structure comprising supporting a pair of side rods in spaced substantially parallel relation in a given fixed plane, forming a succession of notches in said side rods by laterally moving substantially V-shaped tools along a given path in said plane and into said side rods in successive fashion while holding said side rods free of rotational transverse motion to form a succession of notches in said side rods, leading a grid Wire into each of said successive notches prior to formation of the next succeeding notch in a respective side rod moving said side rods longitudinally in said plane to position an unnotched surface opposite said tools, and simultaneously forming each successive notch in the unnotched surface of the rods and sufficiently close to the preceding notch in the respective side rods to cause the material of the side rods to be forced toward the preceding notch whereby said grid wire is secured therein.

Washburn Nov. 28, 1939 Legendre et a1 Oct. 6, 1953 

1. THE METHOD OF MAKING A GRID STRUCTURE COMPRISING SUPPORTING A PAIR OF SIDE RODS IN SUBSTANTIALLY PARALLEL RELATION IN A GIVEN FIXED PLANE, DISPOSING A CUTTING TOOL FOR MOVEMENT ALONG A GIVEN PATH IN SAID PLANE TOWARD AND AWAY FROM A SIDE ROD, MOVING SAID TOOL ALONG SAID PATH IN SAID PLANE INTO ENGAGEMENT WITH SAID ROD TO FORM A NOTCH THEREIN, GUIDING A GRID WIRE INTO SAID NOTCH, MOVING SAID SIDE ROD LONGITUDINALLY IN SAID PLANE TO POSITION AN UNNOTCHED SURFACE OPPOSITE THE TOOL, MOVING THE TOOL 